The long-term objective of this proposal is to develop a novel class of anti-cancer agents based on the plant derived compound parthenolide (PTL). Previous studies have demonstrated that PTL has potent cytotoxic activity against a broad range of malignancies, including cancers of the breast, lung, prostate, colon, liver, kidney, pancreas, brain, and bone. In addition to solid tumor studies, several groups including our own have focused on human leukemia (or related hematologic malignancies). We have demonstrated that PTL is highly cytotoxic to primary human leukemia specimens, but non-toxic to normal blood-forming tissues. Thus, the collective evidence suggests that PTL has broad potential as an anti-cancer agent. However, despite the remarkable properties of this compound, clinical development has been very limited, likely due to the poor pharmacological properties of PTL. Indeed, to our knowledge the only PTL-based compound to reach clinical trial stage work is dimethylamino parthenolide (DMAPT), which we previously developed as an orally bioavailable PTL analog. Thus, going forward we believe that applying novel strategies to create more pharmacologically useful forms of PTL-based agents is a high priority. In the course of performing various chemical modifications of PTL, it was demonstrated that the C-10 methyl group can be hydroxylated by reaction with a suitable oxidizing agent. This reaction changes the geometry of the C-9-C-10 double bond from Z to E to afford a hydroxymethyl 1(10)-cis-parthenolide analogue, a compound previously described as melampomagnolide B (MM-B). Intriguingly, the biological activity of MM-B is identical to PTL, retaining strong specificity for leukemia cells. The presence of the C-10 hydroxymethyl group now creates the opportunity for designing an entirely new class of PTL analog. Thus, in the present application we propose to develop and test novel MM-B-based products. Specifically, the aims of the study will be to 1) synthesize novel water-soluble MM-B prodrugs, 2) perform pharmacological and biological efficacy studies, and 3) perform molecular and cellular characterization of the mechanism of action of MM-B. Taken together these studies will create and validate an entirely new type of anti-cancer agent. In addition, by characterizing the molecular mechanism of action of this novel PTL derivative, it should be possible to further refine strategies for the selective eradication of cancer cells.